Here's a guideline on how to Create Emoticons on Facebook Chat from any profile from the social network. This is very simple to do, so follow this steps.
1-Visit the profile you wish to create as an emoticon.
2-Check out the URL. Find the username or profile ID at the end of the URL such as “VinDiesel” from http://www.facebook.com/VinDiesel, “JoshConstine”, “cocacola”, or “45197362282″
3-Place that name or number in double brackets like [[VinDiesel]]
And that's it! It can't get easier than that
Once you know the user name or id, just enter it into a Facebook Chat or Message field. When you send it, the bracketed number or letters will appear as that person, Page, or event’s current profile picture.